The present invention relates to a rotary circular saw unit, a so-called miter saw or compound miter saw, capable of changing a workpiece cutting angle in which a lowered position of the circular saw can be restricted.
A conventional compound miter saw capable of changing a cutting angle of the saw is shown in FIG. 29.
Referring to FIG. 29, the compound miter saw unit, includes a base 1 on which a workpiece W to be cut is placed. A fence 2 is mounted on the rear, left as viewed, portion of the upper surface of the base 1 and the fence 2 is provided with a center portion 2a and a vertical receiving surface 2b (FIG. 32) for supporting the rear surface of the workpiece W in abutment condition. A rotary table 3 is disposed at substantially the center portion of the base 1, and at a rear portion of the rotary table 3 is disposed a hinge member 4 having a lower portion 16 supported on the side face of the rotary table 3 and an upper portion 17 extending vertically. The hinge member 4 is pivotal in the lateral directions as viewed from the front side of the miter saw unit and is capable of being secured onto the side face of the turntable 3 with a desired angle.
At the upper end portion of the hinge member 4 is supported, in a pivotal manner, a bracket (a circular saw support arm) 7 supporting a main cover 14 and a safety cover 15. A circular saw driving unit 6 is fixed to the side face of the main cover 14 and includes a motor and a reduction gear. The bracket 7 is elevated to a non-cut position by the urging force of an elastic member 8 such as a coil spring. A circular saw 5 is lowered at the time of an actual cutting operation, while gripping the handle till the circular saw 5 enters a circular saw escape slit formed in the rotary table 3 and extending back and forth. At the thus lowered position of the saw 5, the workpiece W is cut by the circular saw 5.
In order to change a miter angle of the circular saw 5 and a bevel angle thereof, the compound miter saw unit of the construction described above has a structure capable of rotating the rotary table 3 in accordance with the miter angle and of pivoting the hinge member in a perpendicular plane (perpendicular to the paper surface) along the lateral direction of the saw unit in accordance with the bevel angle with the pin axis 16a being the center of the pivotal movement. Accordingly, in the compound miter saw unit, the circular saw 5 can be inclined with two degrees of freedom, thus being capable of cutting the workpiece obliquely with a desired angle.
However, the hinge member 4 cannot be swung in the front and rear direction of the unit (left and right direction as viewed in FIG. 29).
Therefore, a setting position of the workpiece W on the rotary table 3 must be changed in accordance with the size of the workpiece W.
FIG. 30 shows a case where a workpiece W1 having a rectangular cross section is cut and when the circular saw 5 is lowered to cut the same, the center of the circular saw 5 coincides with the center of the width direction of the workpiece W1. In this case, since the workpiece W1 has a proper width l1, any extra operations are not necessary. However, in a case where a workpiece W2 having a small width l2 as shown in FIGS. 29 and 31, two abutment pieces P must be disposed between the fence 2 and the workpiece W2 in order to make the center of the workpiece W2 in its width direction coincide with the center of the circular saw 5. The abutment pieces P must be selected in accordance with the width of a workpiece. Moreover, the abutment pieces must be disposed separately from each other in the lateral direction of the base to form a space C therebetween in which a part of the circular saw 5 is accommodated. Therefore, there may cause to scatter cutting chips into ambience during the cutting operation, thus being dangerous.